Selective inhibition of cyclooxygenase‐2 (COX‐2) by 1α,25‐dihydroxy‐16‐ene‐23‐yne‐vitamin D₃, a less calcemic vitamin D analog

Abstract

Inducible cyclooxygenase-2 (COX-2) has been implicated to play a role in inflammation and carcinogenesis and selective COX-2 inhibitors have been considered as anti-inflammatory and cancer chemopreventive agents. 1alpha,25-dihydroxyvitamin D3 (1alpha,25(OH)2D3), the active hormonal form of vitamin D3 also has been considered to be a cancer chemopreventive agent in addition to its important role in maintaining calcium homeostasis. Based on these observations, we studied the direct effect of 1alpha,25(OH)2D3 and one of its less calcemic synthetic analogs, 1alpha,25(OH)2-16-ene-23-yne-D3 on the activity of both COX-1 and COX-2 in an in vitro enzyme assay. Preliminary data indicated that both 1alpha,25(OH)2D3 and 1alpha,25(OH)2-16-ene-23-yne-D3 inhibited selectively the activity of COX-2 with no effect on the activity of COX-1. Out of the two compounds, 1alpha,25(OH)2-16-ene-23-yne-D3 was found to be more effective with an IC50 of 5.8 nM. Therefore, the rest of the experiments were performed using 1alpha,25(OH)2-16-ene-23-yne-D3 only. 1alpha,25(OH)2-16-ene-23-yne-D3 inhibited the proliferation of lipopolysaccharide (LPS) stimulated mouse macrophage cells (RAW 264.7) with a reduction in the expression of COX-2 along with other inflammatory mediators like inducible nitric oxide synthase (iNOS) and interleukin-2 (IL-2). Furthermore, 1alpha,25(OH)2-16-ene-23-yne-D3 also inhibited carrageenan induced inflammation in an air pouch of a rat and effectively reduced the expression of COX-2, iNOS, and IL-2 in the tissues of the same air pouch. In both cases, 1alpha,25(OH)2-16-ene-23-yne-D3 did not show any effect on the expression of COX-1. In summary, our results indicate that 1alpha,25(OH)2-16-ene-23-yne-D3, a less calcemic vitamin D analog, exhibits potent anti-inflammatory effects and is a selective COX-2 inhibitor.

Vitamin D in cancer chemoprevention

“…Vit D and TGF-b share similar effects on cell growth and differentiation (Daniel et al, 2007;Wu et al, 1998). Experimental studies stress that, according to the cell type, Vit D may increase the expression levels of TGF-b and that of its receptors (Chen et al, 2002;Daniel et al, 2007;Koli & Keski-Oja, 1995;Tu et al, 2013;Wu et al, 1997aWu et al, ,b, 1998Yanagisawa al., 1999) or its secretion (Bizzarri et al, 2003;Koli & Keski-Oja, 1995 in the protection of cell from oxidative stress; induction of the expression of numerous isoforms of semaphorins, including SEMA 3B, 3F, and 6D Inhibition of COX-2 expression levels Aparna et al (2008) Repressesion of the WNT antagonist DICKKOPF-4 (DKK4) which promotes invasion and angiogenesis in colorectal cancer cells Pendás-Franco et al (2008b) Immune system Modulation of the expression which encodes for proteins that are crucial for autophagy and for the antimicrobial activity in cells of the innate immune system Hewison (2011) Induction of the expression of cathelicidin (CAMP) and, to a lessen exent, of defensin b2 (DEFB2/HBD2) in different normal and tumor cell types such as colon cancer, acute myeloid leukemia, keratinocytes, human bone marrow cells-derived macrophages, and bone marrow cell Gombart et al (2005) Alteration of the interrelationship between immune cells and cancer cells leading to a significant decrease in the pro-inflammatory cytokines TNF-a and IL-6…”

“…As these molecules may antagonize the proangiogenetic effects of VEGF by a competitive binding to receptor NRP1, this may also partly account for the growth-inhibiting effects of Vit D on prostate cancer cells. An additional mechanism of the preventive effects of Vit D on tumor angiogenesis involves its ability to inhibit COX-2 expression levels (Aparna et al, 2008). COX-2 has been shown to exert indirectly its promoting effects on tumor angiogenesis by increasing the synthesis of HIF-1a protein in cancer cells (Sahin et al, 2009).…”

Vitamin D analogues in colon cancer prevention and care

“…ZK 191784 reduces the histologic score of both chronic and acute colitis [32], whereas Ro 26-2198 delays the onset of colitis and reduces crypt cell proliferation and bleeding severity [33•]. These effects may be mediated by decreases in proinfl ammatory iNOS, interleukin (IL)-2 [34], IL-6, and interferon-γ [32] and increases in the secretion of anti-infl ammatory cytokines such as IL-10 [32]. Analogue treatment also decreases the β-catenin targets COX-2, pERK, and c-myc [33•].…”

The role of Vitamin D in malaria

“…Calcitriol, which reportedly regulates the expression of several key genes that are involved in PG pathways, decreases PG synthesis [144]. Calcitriol and its analogs have also been shown to selectively inhibit the activity of COX-2 [145]. These findings suggest that vitamin D plays a role in the anti-inflammatory processes that are associated with malaria.…”